Rare glimpse into Antarctic underwater world

Under the sea ice in Antarctica

Video transcript

We’re diving under the sea ice in O’Brien Bay, south of Casey research station in East Antarctica.

This is a thriving, colourful world filled with sponges, sea cucumbers, sea spiders, worms, algae and starfish.

Here we are at 30 m below the surface, where the water temperature is a chilly −1.5°C year round, and the sea is covered by ice that is a metre and a half thick for more than 10 months of the year. This ice provides protection from Antarctica’s harsh weather conditions and a stable marine environment that allows biodiversity to flourish.

It is important biodiversity like you see here that is the focus of our research into the effects of climate change and ocean acidification.

Here at the Australian Antarctic Division, we are working hard to ensure the continent remains valued, protected and understood.

The footage was recorded on a camera attached to a Remotely Operated Vehicle (ROV) deployed by scientists under the sea ice at O’Brien Bay, near Casey research station in East Antarctica.

Australian Antarctic Division Biologist, Dr Glenn Johnstone, said the footage was captured while scientists retrieved a SeapHox pH data logger, which has been recording the acidity, oxygen, salinity and temperature of the seawater on an hourly basis since November last year.

“When you think of the Antarctic coastal marine environment, the iconic species such as penguins, seals and whales usually steal the show,” Dr Johnstone said.

“This footage reveals a habitat that is productive, colourful, dynamic and full of a wide variety of biodiversity, including sponges, sea spiders, urchins, sea cucumbers and sea stars.

“These communities live in water that is -1.5°C year round and are covered in 1.5 metre thick sea ice for 10 months of the year.

“Occasionally an iceberg may move around and wipe out an unlucky community, but mostly the sea ice provides protection from the storms that rage above, making it a relatively stable environment in which biodiversity can flourish.”

Dr Johnstone said scientists are only just beginning to understand the amazing biodiversity and complexity of the Antarctic near-shore ecosystem and the threats it is facing into the future.

The Australian Antarctic Program project is the final field component of an experiment designed to determine the impacts of ocean acidification on Southern Ocean sea-floor communities under increasing carbon dioxide emissions.

Project leader, Dr Johnny Stark of the Australian Antarctic Division, said a quarter of the carbon dioxide emitted into the atmosphere is absorbed by the ocean, which increases its acidity.

“Carbon dioxide is more soluble in cold water. Polar waters are acidifying at twice the rate of tropical or temperate regions, so we expect these ecosystems to be among the first impacted from ocean acidification,” Dr Stark said.

“Research shows the pink encrusting algae, known as crustose coralline algae, may decrease in extent in a more acidic future ocean, as it incorporates calcium into its structure, and this becomes harder for organisms to obtain as the acidity of the seawater increases.

“Antarctica may be one of the first places we see detrimental effects of ocean acidification on these organisms.”

Australian Antarctic Division PhD student James Black said the ROV was deployed through a small hole drilled in the sea ice and also collected diatoms and sediment.

Scientists will study the effect of ocean acidification on these communities in laboratories at the Division’s headquarters in Tasmania.

“Even small shifts in the timing of sea ice breakout can alter the composition of communities in these shallow coastal waters so we’re seeking to understand what other impacts there may be in an acidifying ocean,” Mr Black said.